Method for the manufacture of pharmaceutical cellulose capsules

ABSTRACT

A method and apparatus for manufacturing pharmaceutical capsules use an aqueous solution of a thermogelling cellulose ether composition and use capsule body pins and capsule cap pins as molds. The method involves heating the pins, dipping the pins into the solution to cause the solution to gelatinize on the surface of the pins, removing the pins and drying the gelatinized solution on the surface of the pins to form capsule bodies and capsule caps. Pins are heated pre-dip and post-dip to facilitate gelating. Counterflow air is applied to provide drying from the inside. Capsule parts are removed by gripping. Capsule parts may have a thick wall and a stiffening ring.

This application is a continuation application of U.S. Ser. No.08/377/669, filed Jan. 24, 1995, U.S. Pat. No. 5,698,155, which is acontinuation application of U.S. Ser. No. 07/893,091, filed May 29,1992, now abandoned, which is a continuation-in-part application of U.S.Ser. No. 07/708,023 filed May 31, 1991, now abandoned.

TECHNICAL FIELD

The invention relates generally to methods and apparatus used in themanufacture of pharmaceutical capsules.

BACKGROUND OF THE INVENTION

Pharmaceutical capsules presently in general use are made of gelatin andthe techniques for the manufacture of gelatin capsules are welldeveloped. Compositions for cellulose capsules are also well known, butthe first cellulose composition that was used commercially tomanufacture cellulose capsules did not reliably break down in the user'sdigestive system. When this fact was discovered, the commercialmanufacture of cellulose capsules was discontinued. An improvedcellulose composition was later patented by Sarkar and several patentsdisclose methods for manufacturing cellulose capsules from the improvedcellulose composition. However, in the fifteen years since the Sarkarpatent issued, and in spite of many attempts, none have succeeded inmanufacturing cellulose capsules in quantity, using the improvedcomposition, with sufficient uniformity to be suitable for filling inmodern high-speed filling machines. Until the present invention wasmade, cellulose capsules manufactured in quantity from the improvedcomposition suffered imperfections such as wrinkles, starred ends andcorrugations. These imperfections result in capsules either breaking,failing to separate, or jamming in the high-speed filling machine.

Prior Art Gelatin Capsules

Prior art gelatin capsules, as shown in FIGS. 1A, 1B and 1C, are made ina range of sizes including sizes listed in the first column of each ofTables 1 and 2. These tables are copied from the February, 1987Specification Sheet of the CAPSUGEL Division of Warner-Lambert Companyfor its PRE-FIT™, SNAP-FIT™ and CONI-SNAP™ series of hard gelatincapsules. Table 1 shows the external diameter, obtained by opticalmeasurements, of a body and a cap of each size of CAPSUGEL capsule.(Diameter is difficult to measure precisely because of the slightlytapered shape and the flexibility of the gelatin capsule parts.) Table 2shows the target wall thickness of a body and a cap of each type andsize of CAPSUGEL capsule. Table 3, copied from the Scherer LOX-IT™specification sheet, gives the external diameter of the Scherer LOX-ITM™capsule caps and bodies in a range of sizes.

                  TABLE 1                                                         ______________________________________                                        CAPSUGEL CAPSULE PART, EXTERNAL DIAMETER                                      PRE-FIT ™ SNAP-FIT ™ or CONI-SNAP ™                                          Body          Cap                                                     Sizes     Inches   mm         Inches mm                                       ______________________________________                                        000       0.378    9.60       0.394  10.00                                    00        0.324    8.23       0.339  8.60                                     0 el      0.291    7.38       0.300  7.70                                     0         0.291    7.38       0.303  7.70                                     1         0.263    6.68       0.275  6.98                                     2         0.241    6.13       0.252  6.41                                     3         0.221    5.61       0.231  5.88                                     4 el      0.201    5.11       0.212  5.38                                     4         0.201    5.11       0.212  5.38                                     5         0.185    4.70       0.193  4.89                                     ______________________________________                                         Tolerance: ±0.001 (±0.03 mm)                                       

                                      TABLE 2                                     __________________________________________________________________________    CAPSUGEL CAPSULE PART, SINGLE WALL THICKNESS                                  PRE-FIT ™             SNAP-FIT or CONI-SNAP ™                           Body           Cap       Body       Cap                                       Size Inches                                                                             mm   Inches                                                                             mm   Inches                                                                             mm   Inches                                                                             mm                                    __________________________________________________________________________    000  0.0042                                                                             0.107                                                                              0.0044                                                                             0.112                                                                              --   --   --   --                                         ±0.0009                                                                         ±0.023                                                                          ±0.0012                                                                         ±0.030                                                 00   0.0041                                                                             0.104                                                                              0.0042                                                                             0.109                                                                              0.0042                                                                             0.107                                                                              0.0043                                                                             0.109                                      ±0.0009                                                                         ±0.023                                                                          ±0.0012                                                                         ±0.030                                                                          ±0.0009                                                                         ±0.023                                                                          ±0.0012                                                                         ±0.030                             0 el --   --   --   --   0.0041                                                                             0.104                                                                              0.0042                                                                             0.107                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             0    0.0040                                                                             0.102                                                                              0.0042                                                                             0.107                                                                              0.0041                                                                             0.104                                                                              0.0042                                                                             0.107                                      ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             1    0.0039                                                                             0.099                                                                              0.0041                                                                             0.104                                                                              0.0040                                                                             0.102                                                                              0.0041                                                                             0.104                                      0.0008                                                                             ±0.020                                                                          ±0.0010                                                                         ±0.025                                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             2    0.0038                                                                             0.096                                                                              0.0040                                                                             0.102                                                                              0.0039                                                                             0.099                                                                              0.0040                                                                             0.102                                      ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                              3*  0.0034                                                                             0.086                                                                              0.0036                                                                             0.092                                                                              0.0035                                                                             0.089                                                                              0.0036                                                                             0.092                                      ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             4 el --   --   --   --   0.0037                                                                             0.094                                                                              0.0038                                                                             0.096                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             4    0.0034                                                                             0.086                                                                              0.0036                                                                             0.089                                                                              0.0034                                                                             0.086                                                                              0.0035                                                                             0.091                                      ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                                                                          ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                             5    0.0034                                                                             0.086                                                                              0.0036                                                                             0.092                                                                              --   --   --   --                                         ±0.0008                                                                         ±0.020                                                                          ±0.0010                                                                         ±0.025                                                 __________________________________________________________________________     3* SNAPFIT ™ Body Target -- 0.0034 ± 0.0008                        

                  TABLE 3                                                         ______________________________________                                        SCHERER LOX-IT ™ CAPSULE PART DIAMETER                                     Size     0        1        2      3      4                                    ______________________________________                                        CAP      0.301"   0.272"   0.250" 0.230" 0.210"                               DIAMETER*                                                                     (±0.003)                                                                   BODY                                                                          DIAMETER*                                                                              0.289"   0.262"   0.240" 0.220" 0.200"                               (±0.003)                                                                   ______________________________________                                         *DETERMINED AT CUT EDGE                                                  

U.S. Pat. No. 3,399,803 to Oglevee et al. is directed to a hard-shellself-locking pharmaceutical capsule having a cap part and a body part,the parts adapted for machine filling. Oglevee discloses mold pinshaving a uniform taper or candle-shape such as to avoid suction when thepart is removed from the pin and to provide a wedging fit between thecapsule cap and the capsule body. Oglevee also discloses the shaping ofthe cap and body to provide a semi-locked position and a lockedposition. A single groove in the cap and a matching single groove in thebody provide a mechanical lock.

U.S. Pat. Nos. 3,508,678 and 3,664,495 both to Graham et al. disclose acapsule cap having an indent, in addition to a locking groove, whichdefines a prelock position by providing either an elastic friction fitwith the capsule body (U.S. Pat. No. 3,664,495) or a mechanical lockbetween the indent of the cap and the groove in the body (U.S. Pat. No.3,508,678).

U.S. Pat. No. 4,247,006 to Bodenmann et al. discloses a capsule bodyhaving a reduced diameter in the area of its open end, and further thecapsule cap and the capsule body each having an indentation to providefor a positive engagement of the body and the cap.

Prior Art Process for Gelatin Capsules

U.S. Pat. No. 1,787,777 to Colton describes the "Colton" machine used inthe manufacture of gelatin capsules. Key elements in the prior artmanufacture of gelatin capsules are illustrated in FIGS. 1-7. FIG. 1Ashows the parts of a capsule having a body 1 and a cap 2. The parts areshown in FIG. 1B in a prelock position 3 held in position by prelockdimples 4. The parts are also shown in FIG. 1C in a filled position 5held in position by locking rings 6. FIG. 2 shows elements of thetraditional "Colton" capsule manufacturing machine. The elements are agreaser section 21, a dipper section 22, spinners 23, upper drying kiln24, lower drying kiln 26, table section 27 and automatics 28. A pinbar,having thirty pins 31 mounted to a bar 32, is shown in FIG. 3. FIG. 4shows gel 41 formed around a pin 31 to a dip line 42. Also shown is thetrim line (cut-point) 43 and the area 44 on the pin above the dip line.FIG. 5 shows a prior art stripper 51 about to push a capsule part 53 offa pin from the area 44 above the dip line with pushing face 52. A sideview of a prior art stripper having a pivot 61 and a spring 62 is shownin FIG. 6. FIG. 7 shows a knife 71 trimming a capsule part to remove therough edge 72 and create a clean edge 73.

U.S. Pat. Nos. 1,978,829 (to Wilkie), 3,632,700 (to Oglevee), 3,794,453(to Padilla et al.), 4,705,658 (to Lukas) and 4,997,359 (to Lebrun) areall directed to processes for manufacturing gelatin capsules. The Wilkiepatent discloses an apparatus for drying capsules by directing a streamof air at the part of the capsule that contains the most moisture. Afine stream of air passing through a hole in a plate is directed to theclosed end of the capsule so that a greater drying effect is experiencedon the closed ends of the capsule than on the sides of the capsule. Aplate is provided having multiple holes spaced to match the position ofthe pins. The Oglevee patent discloses a method for insuring capsulewall thickness uniformity by measuring the viscosity of the liquid gelsolution in the dipping tank and causing corrective change in viscosityby changing the evaporative exposure or by adding lower viscosity gel tothe tank. The Padilla patent discloses an air duct directing cooling aironto freshly dipped capsule mold pins for improved wall thicknesscharacteristics. The duct is an air conduit for moving cool air upwardlyagainst the rounded ends of the coated pins for uniform flow. The ductencloses a zone surrounding the array of pins. The Lukas patent isdirected to reducing the drying time in the manufacture of hard shellgelatin capsules. Pins are irradiated with microwave energy until thegelatin dries. The Lebrun patent discloses a dipping bath, having aplurality of small wells and an impeller for maintaining the solution inthe wells at a constant temperature. The pins dip into the wells.

Prior Art Capsule Forming Pins

U.S. Pat. No. 4,758,149 to Sauer is directed to a capsule forming pinhaving a cylindrical sidewall and a groove extending around thecylindrical sidewall, the groove having a non-angular cross-sectionalprofile, both the cylindrical sidewall and the groove having a smoothburnished-hardened surface. Sauter discloses in FIG. 3A, item C andcolumn 4, line 45, that a prior-art capsule cap pin for a "0" ("zero")size capsule has a diameter at the cut-point of 0.2973-0.2978 inch(7.551-7.564 mm). The prior-art capsule body pin at the cut-point is0.2848-0.2853 inch (7.234-7.247 mm).

For a range of popular sizes of gelatin capsules, Table 4 shows thenominal cut-point diameter for the prior art body pin and the prior artcap pin used in forming, respectively, the gelatin capsule body and thegelatin capsule cap.

                  TABLE 4                                                         ______________________________________                                        PIN CUT-POINT DIAMETER                                                               Body          Cap                                                      Sizes    Inches   mm         Inches mm                                        ______________________________________                                        00       0.3195   8.12       0.3355 8.52                                      0        0.2855   7.25       0.2975 7.56                                      1        0.2575   6.54       0.2685 6.82                                      2        0.2355   5.98       0.2455 6.24                                      3        0.2155   5.47       0.2255 5.73                                      4        0.1955   4.97       0.2045 5.19                                      ______________________________________                                    

Prior Art Process for Cellulose Capsules

An improved methyl cellulose ether composition that may be used in thepresent invention is disclosed in U.S. Pat. No. 4,001,211 to Sarkar.Sarkar also discloses a process for the manufacture of capsules from hisimproved methyl cellulose ether composition. The improved methylcellulose ether composition disclosed by Sarkar is an aqueous solutionof a thermal gelling methyl cellulose ether composition suitable for usein preparing pharmaceutical capsules by an aqueous dip coating processusing preheated pins and having a methoxyl DS of about 1.5-2.0, a C₂ -C₃hydroxyalkyl MS of about 0.1-0.4, a 2 wt. percent aqueous solutionviscosity of about 2-10 cps at 20° C. and a thermal gel point of about50°-80° C., and a 15-30 wt. percent aqueous solution viscosity of about1,000-10,000 cps at 20° C., said composition having as a 15-30 wt.percent aqueous solution: (A) essentially Newtonian fluid properties asdefined by a power law coefficient, n, of 0.9-1.0 at shear rates ofbetween 0.1-10 sec⁻¹, and (B) a 50 sec gel yield strength of at least150 dynes/cm² at 65° C.

U.S. Pat. No. 4,993,137 to Muto is directed to the manufacture ofcapsules made from the improved methyl cellulose ether composition ofSarkar. Muto discloses a process for gelling the solution by dippingsolution-coated pins into thermally controlled water. In the Mutoprocess, the solution is gelled on the surface of the pins by firstdipping the pins into solution and thereby coating the pins withsolution and then dipping the coated pins into heated water to set thegel.

U.S. Pat. Nos. 2,526,683 (to Murphy), 2,671,245 (to Kath), 3,617,588 (toLangman) and 3,842,242 (to Chisholm) are directed to methods ofmanufacture of capsules from methyl cellulose (the original methylcellulose, not the improved methyl cellulose disclosed by Sarkar). TheMurphy patent is the original patent for the manufacture of methylcellulose capsules. This patent discloses the preheating of pins priorto dipping so that the solution adheres to pins in gelled form, the useof a sequence of different "successively warmer temperatures" throughthe drying kiln, drying using infrared lamps, and cooling by air. Murphyaccomplished a mechanization for the manufacture of cellulose capsules.However this method was found to be inadequate when (later) it wasapplied to the improved cellulose of the Sarkar patent. The Kath patentdiscloses apparatus for manufacturing either gelatin or methyl cellulosecapsules. It discloses the use of tracks and a plurality of pins. Thepins are moved along the tracks and moved, rotated and gyrated as neededthrough the various stations. This patent contains detailed mechanicaldisclosure. The Langman patent is directed to elimination of unwantedthermal gelation in the coating bath by the use of low viscosityhydroxyalkayl cellulose ethers and the rapid immobilization of the dipcoating by induction heating after removal of the pins from the bath.The Chisholm patent is directed to heating the pins prior to dipping anddiscloses apparatus for preheating capsule pins in a "Colton" capsulemachine. A tray is provided containing spheroidal particles heated to apredetermined temperature. The pins are dipped into the heated particlesjust prior to being dipped in the solution.

The prior art for the manufacture of pharmaceutical capsules from theimproved thermogelling methyl cellulose ether compositions disclosed inthe Sarkar patent contain a number of unresolved problems. Theseunresolved problems include skinning, wrinkling, starred ends andcorrugations in the wall of the capsule parts, and damage to the capsuleparts occurring during removal from the pins. These problems causebreaking, failure to separate or jamming in the high-speed fillingmachines. There is no discussion in the prior art of the source of theseproblems.

None of the above mentioned patents disclose a method for makingcellulose capsules of sufficient uniformity and rigidity that they maybe filled on modern high-speed capsule filling machines. This uniformityand rigidity has now been accomplished using the process and capsuleimprovements that are the subject of the present invention.

SUMMARY OF THE INVENTION

A method and apparatus for manufacturing pharmaceutical capsules, eachcapsule consisting of a capsule body and a capsule cap, uses an aqueoussolution of a thermogelling cellulose ether composition and uses capsulebody pins and capsule cap pins as molds. A group of pins is mounted on abar. The method involves heating the pins; dipping the pins into thesolution to cause the solution to gelatinize on the surface of the pins;removing the pins from the solution; drying the gelatinized solution onthe surface of the pins to form capsule bodies and capsule caps; andremoving the capsule bodies and capsule caps from the pins. In oneembodiment of the present invention, the time interval between heatingand dipping may vary from bar to bar. To compensate, each bar is heatedto a different temperature according to the time interval associatedwith the bar. Pins may be heated by radiant energy or by hot air or viathe bar at a plurality of thermally isolated stations. Additionally aportion of the bar may be heated to a predetermined temperature. Theprocess includes heating the pins before dipping and heating the pinsafter dipping. The dipping dishes for capsule bodies and capsule capsare spaced apart farther than in the traditional Colton machine and apre-dip heating area is located between the dipping dishes. After thepins have been dipped and removed from the solution they are heatedagain to further gelatinize the solution on the surface of the pins.Drying the pins includes providing counterflow movement of air throughan enclosure over the pins such that the pins initially encounterrelatively humid air and, as they become drier, they encounterincreasingly drier air. Also, the pins are heated so that the capsulebodies and capsule caps are dried from the inside-out. Removing thecapsule parts from the pins involves gripping the capsule parts betweenopposing gripping surfaces. In one embodiment the capsule parts have athicker wall than the equivalent size gelatin capsule and capsule bodiesinclude a stiffening ring.

Problems in the prior art are overcome in one embodiment of the presentinvention as follows. In preheat, to compensate for differential coolingfrom some bars waiting longer than others to dip, thermally isolatedheating elements are provided below the bars and radiant heaters areprovided above the bars to allow selective heating of bars or portionsof bars to eliminate temperature differences at the time of dip. Toallow preheat in the dipper area without the problems associated withChisholm's heated particle method, the dipping dishes are moved awayfrom the centerline and thermal convection heaters and radiant heatersare inserted. For the same purpose, thermal conduction heating via theback of the bars is also provided. To achieve the level of uniformitynecessary for high-speed filling and to eliminate the skinning over andwrinkling associated with the outside-in drying of the prior art due toair blowing directly over the pins, inside-out drying is provided.Post-dip heating is used in addition to pre-dip heating. Post-dipheating continues the gelling process after dip, assures rapid firmingof the cellulose film, and supports inside-out drying. To avoid theuneven or excessively rapid drying that causes deformation in the priorart, an appropriate relationship is maintained between water vaporpressure in the capsules and water vapor pressure in the surrounding airthrough the drying process. A fully enclosed drying kiln is provided tosupport inside-out drying, humidity control of air surrounding the pins,and energy efficiency. To avoid damaging the open end of the capsulepart during removal of the part from the pin, which often occurs whenthe prior art technique is used on cellulose capsule parts, a gripper isprovided. To eliminate the jamming in the filling machines due tooversize parts, the pin is undersized to compensate for the unexpecteddifferential in shrinkage between the cellulose capsule and the gelatincapsule. To avoid malfunction in filling machines caused by flexibilityof the capsule part and deformation out of round, a pin is furtherundersized to allow a thicker capsule wall. Also the body pin adds anextra circumferential reinforcing ring to the capsule body between thelock ring and the dome.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C show a prior art capsule body and cap.

FIG. 2 shows the elements of the traditional (prior art) capsulemanufacturing machine.

FIG. 3 shows pins mounted on a pinbar (prior art).

FIG. 4 shows a pin dipped to a dip line (prior art).

FIG. 5 shows a prior art stripper pushing a capsule part off a pin.

FIG. 6 shows a prior art stripper.

FIG. 7 shows a knife trimming the rough edge of the capsule (prior art).

FIG. 8A shows a schematic embodiment of the present invention, includinga preheat section and a kiln enclosure.

FIG. 8B is a schematic cross-sectional elevation view of the drying kilnshowing the enclosure and air flow.

FIG. 8C shows location of the heating elements and fans in the enclosureof FIG. 8B.

FIG. 8D shows a schematic plan view of all sections between the splitdeck and the spinners.

FIGS. 8E and 8F show two elevation views of the convection preheatsystem.

FIG. 8G shows the insulation box for the table section.

FIG. 9 shows a schematic embodiment of the present invention, includinglocations of the several preheat sections.

FIGS. 10A and 10B show temperature sensors and under-deck heatersassociated with the split deck.

FIG. 10C shows a group of cap pinbars and the corresponding group ofbody pinbars.

FIG. 10D shows the split deck layout for the bars of FIG. 10C.

FIG. 11 shows non-contact temperature sensors and overhead heatersassociated with the split deck.

FIGS. 12 and 13 show a plan and elevation view respectively of a dippersection preheat arrangement.

FIGS. 14A and 14B show two views of a preheater with air ducts forselectively heating pins.

FIG. 15 shows the gel dish temperature control scheme.

FIGS. 16A, 16B and 16C show apparatus for heating the pins through thepinbar to permit post-dip gelling in the spinner section and "inside-outdrying" in the drying kiln.

FIG. 17 illustrates the process of removing the capsule part from thepin.

FIG. 18 gives detail of the stripper of FIG. 6 as modified for thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides improvements over the method ofmanufacture of pharmaceutical capsules disclosed in U.S. Pat. No.4,001,211 to Sarkar. The Sarkar cellulose composition is particularlysuited for preparing pharmaceutical capsule shells which dissolve at arate comparable to gelatin capsules. Delay release characteristics canbe obtained by incorporation of a less water-soluble cellulose such asethyl cellulose as described by Greminger and Windover in U.S. Pat. No.2,887,440. In a preferred embodiment, the present invention uses theimproved thermogelling methyl cellulose ether compositions disclosed inthe Sarkar patent, including a thermal gelling methyl cellulose ethercomposition suitable for use in preparing pharmaceutical capsules by anaqueous dip coating process using preheated pins and having a methoxylDS of about 1.5-2.0, a C₂ -C₃ hydroxyalkyl MS of about 0.1-0.4, a 2 wt.percent aqueous solution viscosity of about 2-10 cps at 20° C. and athermal gel point of about 50°-80° C., and a 15-30 wt. percent aqueoussolution viscosity of about 1,000-10,000 cps at 20° C., said compositionbeing further characterized by having as a 15-30 wt. percent aqueoussolution: (A) essentially Newtonian fluid properties as defined by apower law coefficient, n, of 0.9-1.0 at shear rates of between 0.1-10sec⁻¹, and (B) a 50 sec gel yield strength of at least 150 dynes/cm² at65° C.

The apparatus of the present invention, in a preferred embodiment, isbased on the type of capsule machine disclosed in U.S. Pat. No.1,787,777 to Colton and U.S. Pat. No. 2,671,245 to Kath. The machinethat was modified to embody the present invention was a "Colton" capsulemachine manufactured by R & J Engineering Corporation, 100 HansenAvenue, Kitchener, Ontario, Canada N2C 2 E2.

1. General

The present invention provides a production process and a fullymechanized production apparatus that may use the modified cellulose inU.S. Pat. No. 4,001,211 to Sarkar for manufacturing pharmaceuticalcapsules of sufficient uniformity and rigidity that they may be filledon modern high-speed capsule filling machines. Capsules may be made in arange of sizes similar to the range of sizes in Tables 1-3. For a givencapsule the capsule bodies and capsule caps have different dimensions asillustrated for the prior art capsules in FIGS. 1A-1C. The processinvolves a series of steps performed by one machine. Each capsule partis made by dipping a hot stainless steel pin into a cellulose gelsolution and drying the gel to form a hard film over the pin. The pinsare mounted in a row on a bar as illustrated in FIG. 3. FIG. 4 shows apin with a gel coating. Body pins are mounted on one set of bars and cappins are mounted on a corresponding set of bars so that correspondingbodies and caps may pass through the entire process in phase with eachother and emerge from the process facing each other positioned forassembly as a capsule.

The process, in a first embodiment, is arranged so that the bars travelin a continuous loop illustrated in FIG. 8A. The process steps in thisembodiment are:

Preheating the pin bars (Preheat Section);

Oiling the pins (Greaser Section);

Dipping the pins into cellulose solution (Dipper Section);

Spinning the coated pins (Spinner Section);

Drying the gel (Upper and Lower Drying Kilns);

Positioning the pinbars so that corresponding caps and bodies face eachother (Table Section);

Removing the caps and bodies (Automatics);

Trimming the caps and bodies (Automatics);

Joining caps and bodies into prelock position (Automatics).

Removing and trimming the caps and bodies is illustrated in FIGS. 17 and7 respectively. Joining the caps and bodies to form a capsule in aprelock position, ready for filling, is illustrated in FIGS. 1A and 1B.FIG. 1C shows a capsule with the lock ring engaged as it would be afterfilling.

The process is similar to the process for manufacturing gelatin capsulesexcept that the process for manufacturing gelatin capsules involvesdipping cold pins into a gel whose temperature is above the gel pointwhereas the process for manufacturing cellulose capsules involvesdipping hot pins into a gel whose temperature is below the gel point.Novel aspects of the present invention include process steps designed toovercome the peculiar difficulties of manufacturing cellulose capsulesusing the cellulose composition disclosed in the Sarkar patent. In apreferred embodiment, the present invention uses temperature, humidityand air flow control components including heaters, sensors, enclosures,fans and thermal isolation components. This embodiment also uses pinsthat are narrower than the pins used in the prior art and in oneembodiment provides a capsule body having a stiffening ring.

2. Temperature Control

Capsules must have consistent wall thicknesses from capsule to capsulefor them to be filled on high-speed filling machines. To accomplishthis, the temperature of the stainless steel pin molds, which areattached to a pinbar, must be controlled throughout the process. Thepins must be heated uniformly so that a repeatable amount of gel ispicked up on each pin in the dipping operation. While several patentsspeak about the need to heat the pinbars prior to dip, none address thecritical need for heating all pins from bar to bar to substantially thesame temperature to produce capsules sufficiently uniform for high-speedfilling. In the process of making cellulose capsules on a traditional"Colton" capsule machine, some pinbars must wait longer than others todip. The present invention includes compensatory temperature controlwhere some bars or parts of bars are independently heated to highertemperatures than others to compensate for the longer wait these barshave before dipping and for the different ambient temperature (due totemperature gradients within the machine) experienced during the wait,and also for temperature gradients resulting from differing pin, pinbar,and/or deck conductivities. The compensatory temperature control systemoperates to maintain predetermined temperatures in the bars prior todipping to achieve substantially equal temperatures in the pins at thetime of dipping. Compensatory temperature control can be provided by avariety of equipment configurations as follows:

a) Compensatory Sensing and Heating on Drying Decks

Groups of twenty bars move from drying station to drying station on ametal deck. Since bars sit in each position for some time before moving,heating sources may be positioned under the deck and also over the barsin such a manner so that heat may be applied to raise the temperature ofselected bars in the group of twenty. The last station of the lowerdeck, just prior to the table section, provides separate heating areasthat are thermally isolated from each other so as to heat bars andportions of bars selectively. When bars leave the drying decks and loadonto the table section, they are fed one at a time into the centerelevator for processing one at a time in the automatics section. Thelast bar in the group of twenty must wait the longest. By selectivelyheating these later bars to higher temperatures, the delay before dip iscompensated for. At time of dip, these later bars will have atemperature substantially equal to the earlier bars that had less timeto cool down before entering the dipping station.

b) Insulation and Compensatory Heating in Table Section

After leaving the drying decks, bars are fed from the deck onto a TableSection which takes the group of twenty bars and feeds them one at atime into the T-slides for continued processing. In this Table Sectionheat can be applied by any means to maintain the later bars at therequired temperature so that they do not cool as they wait their turnfor further processing. The table section is covered with an insulatedbox with heat sources to maintain temperatures and further accommodatethe later bars so that all bars reach the dipping bath at substantiallythe same temperature.

c) Compensatory Sensing and Heating to Adjust for Temperature Variationsfrom the Front of the Bar to the Back of the Bar

Because of the temperature gradients within the machine, there is noguarantee (with the prior art machines) that the temperature along thelength of a given bar will be constant. Variation of temperature alongthe length of the bar would cause temperature variation pin to pin. Forexample, the front end of the bar may be cooler than the back end, andthus pins in the front are also cooler. In the present invention, thedifferential heating mentioned above also may be set up to compensatefor temperature gradients within the machine in order to ensureuniformity of temperature, pin to pin, along a given bar. This isaccomplished by applying heat selectively via the deck supporting thebars and from overhead radiant heaters. The last station of the lowerdeck, just prior to the table section which delivers bars one at a timeto the automatics, is known as the "split deck." Heating from eachthermally predetermined temperature profile that results in thetemperature of all pins being equal when they reach the dipper.

3. Novel Approaches to Drying Cellulose Capsules After the DippingProcess

a) Counterflow Drying and Enclosed Kilns

Drying techniques used in prior art mechanized capsule manufactureinvolves overhead kilns with perforations on the bottom plate throughwhich air blows over the capsules. The air then escapes into the room.The present invention uses enclosed kilns where air is only introducedat the pin-exit end of the lower kiln (i.e., the end of the dryingprocess) and then proceeds in a counterflow direction to the pinbarmovement, all air being contained in the enclosed kilns and beingremoved at the pin-entry end of the top kiln, which is the beginningpoint of the drying process. The pins, on entering the drying process,encounter relatively humid air and, as the pins move through the dryingprocess and become drier, they encounter increasingly drier air.

b) Inside-Out Drying

All capsule drying was formerly accomplished by drying from the outsideby blowing air over the pins from above. The present invention driesfrom the inside-out by using heat both from beneath the deck and alsofrom above the pins (radiant or infrared, microwave, etc.) to heat thepins themselves, thus driving the moisture out from the inside. Thisgives more uniform capsules free from defects of wrinkles andcorrugations common with outside-in drying, and avoids the casehardening or skinning over that occurs in cellulose capsule productionby drying with air alone.

4. Novel Ways to Preheat Pinbars Prior to Dipping

a) Adding a Separate Preheat Section to the Process Prior to Dip

Heating the pins is necessary so that gel will be formed on the pins inthe dipping bath. In the Murphy patent, pins are heated as a byproductof the drying. The hot air used to dry the capsules also heated thepinbars (in a way that is uncontrolled with regard to pin-temperaturerequirements for dipping) before capsule removal and redipping. The onlymention in the prior art of controlled preheating is the Chisholm patentwhich suggests that the pins be immersed in a bath of hot beads prior todip. In practice the Chisholm approach is not feasible because of theproblems discussed hereinbelow under "Analysis of the Problems in thePrior Art." For example, removal of capsules made from the improvedcellulose from pins is even more difficult than removal of capsules madefrom gelatin from pins (also very difficult) because the improvedcellulose forms a weaker and more flexible film. Because the walls ofthe capsule parts lack sufficient rigidity to be removed easily, thelubricant layer must be administered carefully and left intact. Thepresent invention provides a preheat area whose specific purpose is toapply heat to the pins without contact in preparation for dipping. Thispreheat area can be in any or all of the following places:

a) On the drying decks, or at the end of the drying decks and before thetable section.

b) On the table section.

c) Between the table section and the automatic section.

d) After the automatic section and before the greasing section.

e) After the greasing section and before the dipping section by meansthat do not contact the pins.

f) In the dipping section by means that do not contact the pins, such asradiant heat, hot air, induction heat, contact elements to back side ofbar, or other suitable method. Another problem with the Chisholmapproach is that the traditional capsule machine does not have room toaccommodate the procedure he recommends because of the close proximityof the dipping dishes to the centerline of the machine. Thus the presentinvention also includes extending the dipper section on both cap andbody sides to move the dipping dishes further out from the centerline ofthe longitudinal axis of the traditional capsule machine. This allowsspace to accommodate a preheat process that does not involve contactwith the pins.

5. Description of Apparatus

FIG. 8A shows some elements of a first schematic embodiment theapparatus of the present invention, most notably a preheat section 80, akiln enclosure 81, with air ingress aperture 82 and air egress aperture83, an insulated, heated table section enclosure 84, an insulated,heated spinner section enclosure 85 and a dipper section having abuilt-in preheat portion 86. The arrows in FIG. 8A indicate thedirection of pin movement through the machine.

FIG. 9 shows a schematic embodiment of the apparatus of the presentinvention including several preheat sections, as follows: in the dryingkiln 80, between the drying kiln and the table section 91, on the tablesection 92, between table and automatics 93, between automatics andgreaser 94, between greaser and dipper 95, and in the dipper section 96.

FIG. 8B shows the overall physical shape of kiln. The overall length L1of the machine, i.e., the length of the upper kiln, is 44 feet (13.4 m).This is longer than the traditional Colton machine, the upper kilnhaving been extended by three table-lengths to accommodate a new preheatsection 94 (shown in FIG. 8C) between the automatics and the greaser.The height H1 of the upper kiln is 2 feet (61 cm). The length L2 of thelower kiln is 26 feet (7.9 m). The height H2 of the lower kiln at thesplit deck is 2 feet (61 cm) and the height H3 of the lower kiln at theback elevator is 1 foot (30 cm). The walls of the kiln are insulated.The kiln comprises an enclosure 81 having air entrance duct 801 and airexit duct 802. The direction of air flow is indicated by arrows 803.FIG. 8C locates the two 6-inch (152-mm) circular duct fans 805 and thesingle 10-inch (254-mm) duct fan 807, all mounted in the lower kiln 26,which power the air flow though both kilns. The two duct fans 805 aremounted side by side so as to blow air in a direction substantiallyparallel to the axis of the lower kiln toward the back of the machine,drawing air from inlet 801 and driving it into the upper kiln 24. Eight9-inch (229-mm) agitator fans 804 in the upper kiln are arranged in fourpairs of side by side fans, each pair directed to blow air downwardlyonto the pins so as to speed local drying of the gel with agitated(i.e., temperature-equalized) air. Three 9-inch (229-mm) fans 806similarly mounted in the lower kiln dry the pins further.

Heat for inside-out drying and preheat is supplied by a series of five22 inch by 17 inch (56 cm by 43 cm) radiant panels 808 mounted directlyabove the moving pinbars in the lower kiln. General preheat of thepinbars in the split deck position is provided from above by a 22 inchby 17 inch (56 cm by 43 cm) group of radiant panels 809 directly abovethe pinbars and preheat is applied selectively to portions of pinbars byconduction from the split deck assembly 810 that supports the pinbars. A"dome-setter" radiant panel 811 is provided for post-dip heating tofacilitate post-dip gelling and inside-out drying.

The fan and heater configuration described above applies to one side,cap or body, and, in this respect, the cap and body sides aresubstantially identical, except that they are the mirror image of eachother.

Inlet air temperature to the kiln is controlled in the range 125°-180°F. and is preferably 160° F. Absolute humidity of the air at the inletis controlled in the range 0.006-0.012 lb moisture/lb air (0.6-1.2percent) and is preferably 0.009 lb moisture/lb air (0.9 percent). Airflow rate through the body side of the kiln is 63 feet/min (0.32 m/sec)measured at the 8 inch (203 mm) body side inlet duct. The correspondingflow rate through the cap side kiln measured at a cap side inlet duct ofthe same size is 7 feet/min (0.036 m/sec). Within the kiln the flowingair is cooled by evaporative cooling and is heated by heat from the barsand from the radiant panels. The temperature profile found to provideacceptable capsule parts is given in Table 5. Heat from the radiantpanels and thermal conduction heaters is adjusted to maintain thepredetermined temperatures of Table 5. Pressure drop across the kiln is0.020 inches of water (0.005 kPa) (body side) and 0.005 inches of water(0.012 kPa) (cap side). This indicates how much greater the air flowrate through the body side is than the air flow rate through the capside.

                  TABLE 5                                                         ______________________________________                                        ACCEPTABLE AIR TEMPERATURE PROFILE                                                       Body Kiln      Cap Kiln                                            Location   Air Temperature                                                                              Air Temperature                                     in Kiln    °F.                                                                             °C.                                                                              °F.                                                                           °C.                               ______________________________________                                        A          111      43.9      111    43.9                                     B          109      42.8      108    42.2                                     C          110      43.3      107    41.7                                     D          110      43.3      106    41.1                                     E          111      43.9      104    40.0                                     F          114      45.6      104    40.0                                     G          120      48.9      105    40.6                                     H          123      50.6      112    44.4                                     I          142      61.1      140    60.0                                     J          151      66.1      159    70.6                                     K          149      65.0      147    63.9                                     ______________________________________                                    

FIGS. 10A and 10B show temperature sensors and under-deck heaters forpreheat on the split deck in the drying kiln. FIGS. 10A and 11 givedetails of split deck 810 and radiant panel 809 respectively from FIG.8C. FIG. 10A shows sensors 104 mounted in deck 101. Heaters 103 aremounted under the deck. Both sensors and heaters are electricallyconnected to controllers 105 which maintain the predeterminedtemperatures given in Tables 6A and 6B. The deck itself contains thermalisolators 102, so that the several sections of deck beneath a givenpinbar are thermally isolated one from another. Cap pinbars move ingroups of twenty from station to station approximately every 40-70seconds in the drying kilns and body pinbars do likewise. The directionof movement of the pinbars is shown by the arrows in FIG. 10C. Such agroup of pinbars has a length of 22 inches (56 cm), the length of onepinbar, and a width of 17 inches (43 cm), the width of twenty pinbars.Supporting the pinbars in the last station of the drying kiln is thesplit deck shown in plan view in FIG. 10D. The thermal isolators 102 andthe portions of the deck 101 enclosed by the thermal isolators are alsoshown in cross-section elevation view in FIG. 10A. Selective heating ofdifferent portions of twenty pinbars to compensate for pre-dip dwelltime and for temperature gradient in the machine is achieved bycontrollers 105 controlling each of the several enclosed deck portionsat a predetermined temperature. A temperature profile for a preferredembodiment of the present invention is given for each enclosed deckportion 101 of FIG. 10D in Table 6A for the cap side and Table 6B forthe body side. The dimensions of the enclosed deck portions 101 in FIG.10D are given in Table 7.

                  TABLE 6A                                                        ______________________________________                                        CAP SIDE SPLIT DECK TEMPERATURE PROFILE                                       A            B          C          D                                          °F. (°C.)                                                                    °F. (°C.)                                                                  °F. (°C.)                                                                  °F. (°C.)                    ______________________________________                                        1      306 (152) 251 (122)  235 (113)                                                                              267 (131)                                2      181 (82.8)                                                                              178 (81.1) 153 (67.2)                                                                             174 (78.9)                               3      193 (89.4)                                                                              165 (73.9) 135 (57.2)                                                                             142 (61.1)                               ______________________________________                                    

                  TABLE 6B                                                        ______________________________________                                        BODY SIDE SPLIT DECK TEMPERATURE PROFILE                                      A            B          C          D                                          °F. (°C.)                                                                    °F. (°C.)                                                                  °F. (°C.)                                                                  °F. (°C.)                    ______________________________________                                        1      246 (119) 191 (88.3) 252 (122)                                                                              288 (142)                                2      213 (101) 125 (51.7) 193 (89.4)                                                                             154 (51.1)                               3      209 (98.3)                                                                              195 (90.6) 273 (134)                                                                              261 (127)                                ______________________________________                                    

                                      TABLE 7                                     __________________________________________________________________________    CAP AND BODY SIDE, DECK SECTION DIMENSIONS                                    A           B        C        D                                               inch (mm)   inch (mm)                                                                              inch (mm)                                                                              inch (mm)                                       __________________________________________________________________________    1  3 × 4.sup.  (76 × 102)                                                     5 × 4.sup.  (127 × 102)                                                    5 × 4.sup.  (127 × 102)                                                    3 × 4.sup.  (76 × 102)              2  3 × 10 (76 × 254)                                                          5 × 10 (127 × 254)                                                         5 × 10 (127 × 254)                                                         3 × 10 (76 × 254)                   3  3 × 4.sup.  (76 × 102)                                                     5 × 4.sup.  (127 × 102)                                                    5 × 4.sup.  (127 × 102)                                                    3 × 4.sup.  (76 × 102)              __________________________________________________________________________

FIG. 11 shows non-contact temperature sensors and overhead radiantheaters for general preheat on the split-deck in the drying kiln, detail809 of FIG. 8C. Non-contact sensors 111 measure the temperature of thepins (or local area of pinbar) from above. Overhead radiant heaters 112are mounted to the thermal enclosure 113. Controllers 106 are used (inconjunction with controllers 105) to maintain the predeterminedtemperatures of Tables 6A and 6B on the split deck.

Additionally, hot air may be used for heating in the split deck area.

FIG. 8G shows the insulation box 831 for preserving preheat in the tablesection 27. The box has a top and only two sides, one side being omittedto allow a group of twenty bars to enter and another side being omittedto allow bars to exit (in a direction transverse to their length) one ata time.

FIG. 8C locates (schematically) the table section 27, the automatics 28,the convection preheat section 94, the greaser section 21, the dippersection 22 and the spinners 23. The convection preheat section 94includes up to three convection heat systems 812 on each side. Arrows813 indicate the direction of flow of heated air across the pinbar afterthe pinbar has left the automatics where capsules were removed andbefore the pinbar enters the greaser section 21 and the dipper 22. Thelocation of each of the six convection preheat systems 812 is shown inFIG. 8D between automatics 28 and greaser section 21. The convectionpreheat system is shown in greater detail in FIGS. 8E and 8F. FIG. 8Eshows the squirrel cage blower 821, the heating element 822, the supplyduct 823, the pinbar 824, the pin 825 and the return duct 826. Toaccommodate the convection preheat section 94, the original Coltonmachine was extended by three table-lengths, i.e., the upper kiln wasextended by three table-lengths and the greaser section was moved threetable-lengths away from the automatics. In a preferred embodiment, fourconvection preheat systems are used, two on each side. FIG. 8D alsoshows a schematic plan view of all sections between the split deck 810and the spinners 23, including the accumulators 832 and the finalpreheat section 95, whose location necessitates that the dishes arelocated farther apart than they are in the traditional Colton machine.

Lubrication used in the greaser section 21 consists of a mixture oflight mineral oil (59 percent), stearic acid (16 percent), calciumstearate (16 percent), and lecithin (9 percent). A very small measuredquantity is delivered by a metering pump to a felt or brush whichapplies the lubricant directly to the pins. Then a felt-lined barreldistributes the lubricant uniformly over the pin surface.

FIGS. 12 and 13 show a plan and elevation view respectively of a dippersection preheat arrangement. There is symmetry about line A--A exceptthat capsule bodies are on one side and capsule caps are on the other.Body pinbars and cap pinbars slide into the dipper section preheat areain T-slides 121 and drop onto guide rails 124. The dipper dishes arespaced apart to allow an area for the final preheat section 95. See alsoFIG. 9. Heated air is blown across the pinbars via inlet ducts 123 andpreheat hoods 122. The pinbars, leaving the preheat area, are dipped ingroups of five in the dipping dish 125 and spun in the spinners 23within an enclosure 161.

FIG. 13 shows a group of five bars in the accumulator 832 (five barshaving fallen from the T-slides one at a time until five bars areaccumulated in the accumulator). This group of five bars moves tostation 131 in the final preheat section 95 where final preheat isapplied. In an alternative embodiment, one that eliminates the need forpreheating pins according to a time interval to compensate for differentdelay times between preheat and dipping, the dishes are moved apartfurther to accommodate a sufficient number of stations 131. In thisembodiment all preheat is performed between the accumulator and thedishes and is performed without disturbing the layer of grease that wasapplied to the pins on the greaser. Heat is preferably applied bythermal convection from hot air flowing over the pins as shown in FIG.13, or by radiant heat. Heat may also be applied by moving a conductingbar into contact with the top surface of the bars, the pins pointingdown as shown in FIG. 13. Alternatively, induction heating may be used.

FIGS. 14A and 14B show two views of a preheater with air ducts forselectively heating pins in the T-Slides. Air for heating the pinspasses through supply ducts 141 and return ducts 142. The localtemperature of the pinbar is measured by non-contact sensor 143. This isan alternative to the convection preheat section of FIGS. 8E and 8F.

FIG. 15 shows the schematic for control of the dish temperatures. Water157 is pumped by circulating pump 151 through a chiller 152 and a heater153. The heater is controlled by a PID controller 154 connected to atemperature sensor in the body dish 155. After the water leaves theheater, it flows through jackets around both the body dish 155 and thecap dish 156. The temperature in both dishes is controlled to 81° F.±1°F. (27.2° C.±0.6° C.). Body pins should enter the dish at a temperatureof 152° F. (66.7° C.) (range 144° F.-156° F. (62.2° C.-68.9° C.)) andcap pins at a temperature of 151° F. (66.1° C.) (range 149° F.-156° F.(65.0° C.-68.9° C.)). After a pin has been dipped, its temperatureshould be in the range shown in Table 8.

                  TABLE 8                                                         ______________________________________                                        PIN TEMPERATURES AFTER DIPPING                                                               Optimum   Minimum   Maximum                                    Temperature    °F. (°C.)                                                                 °F. (°C.)                                                                 °F. (°C.)                    ______________________________________                                        Location                                                                      Table Load Body    124 (51.1)                                                                              123 (50.6)                                                                            126 (52.2)                               (Spinner)  Cap     122 (50.0)                                                                              121 (49.4)                                                                            124 (51.1)                               Table 1 of Body    --        119 (48.3)                                                                            121 (49.4)                               Upper Deck Cap     --        120 (48.9)                                                                            124 (51.1)                               ______________________________________                                    

FIGS. 16A, 16B and 16C show apparatus for heating the pins through thepinbar to permit post-dip gelation in the spinner section and"inside-out drying" in the drying kiln. The spinner section is enclosedand heat is applied to the pins to cause continued gelation andinside-out drying. Heat is applied in the spinner section by blowing hotair over the pins via ducts 163 and 164 and by heating the pins fromradiant panels 162 mounted to the walls of the enclosure 161. Panels 162are substantially parallel to the longitudinal axes of the bars. It hasbeen found that using a pin temperature at dipping that is cooler thanthe temperature used by Murphy, and heating the pins after dipping tocontinue gelation, provides a better consistency and fewer defects inthe finished capsule. Heat applied to the pinbar in the drying sectiondrives moisture from the inside-out as shown in FIGS. 16B and 16C(inside-out drying). Arrows in FIG. 16C in the bar and pin indicate flowof heat. Arrows in FIG. 16C in the gel and in the air indicate flow ofmoisture. Inside-out drying prevents the formation of "skin" on theouter surface of the capsule that can occur when drying from the outsidewith blown air alone.

FIG. 17 illustrates the process of removing the capsule part from thepin. A gripper 171 (modified stripper) pivots about pivot 172, whendriven by wedge 173, to grip the capsule part 174 prior to sliding itoff the pin. The gripper has opposed gripping faces.

FIG. 18 gives details of the gripper of FIG. 6. The gripping faces 181may be provided with raised ridges or rows of teeth (which may belongitudinal or circumferential to the axis of the pin), or have surfacecomposition or texture, so as to grip the capsule.

6. Pin Size

An important factor in achieving production quantities of capsule bodiesand caps that will run problem-free in high-speed filling machines is tomeet close specifications, especially on external dimensions. Forexample, if the external diameter of each capsule part is even slightlytoo large, caps and bodies will not consistently separate in the fillingchamber because they are too tight a fit. The external diameter of acapsule part is determined by the diameter of the pin mold, theshrinkage of the capsule material after removal from the mold, and thethickness of the capsule wall. The thickness of the capsule wall dependson a number of factors including the initial moisture content andviscosity of the gel and the drying conditions. Accordingly, it isrecommended, for the manufacture of a cellulose capsule part, to use apin whose diameter is undersized compared to the capsule pin for thecorresponding size gelatin capsule part. For example, for themanufacture of a "0" size cellulose capsule part it is recommended touse a capsule pin whose diameter is undersized by an amount in the rangeof approximately 0.002-0.006 inch (0.05-0.15 mm) or approximately 0.004inch (0.1 mm) compared to the capsule pin for manufacture of a "0" sizegelatin capsule part. For other capsule sizes, it is recommended thatthe pin diameter be undersized proportionately. From Table 4, thecut-point diameter of the prior art capsule cap pin is 0.2975 inch (7.56mm) so a reduction range of 0.002-0.006 inch (0.05-0.15 mm) represents areduction range of 0.7%-2.0% and a reduction of 0.004 inch (0.1 mm)represents a reduction of 0.13%. For forming capsule parts for capsuleshaving thicker walls and the same external diameter, the pin diametermay be reduced further as discussed under "Increasing Capsule Stiffness"hereinbelow.

7. Cooling the Dipping Dishes

Passive cooling was found to be insufficient to dissipate the heatdelivered to the dipping dishes by the entry of a succession of hotpins. In the prior art machines used to make gelatin capsules thisproblem cannot arise because cold pins are dipped into a hot gel. Inthese prior art machines, a jacket having pipes is used to pass hotwater to maintain the temperature of the dipping dishes. A similarjacket is used in the present invention except that in the presentinvention the jacket is used for cooling. The jacket includes pipes thatcarry cooling water for removing heat from the dipping dishes so as tocontrol the temperature of the solution in the dipping dishes and themaintain the solution at a substantially constant predeterminedtemperature.

8. Increasing Capsule Stiffness

Cellulose capsules made from the improved methyl cellulose ethercomposition disclosed by Sarkar are found to be less rigid than gelatinor earlier cellulose capsules of an equivalent shape, size and wallthickness. Also, it is essential that the capsule parts retain theirshape in order to pass freely through the high-speed filling machine.For these reasons it has been found beneficial to increase the wallthickness of the capsule parts without increasing the external diameterof the capsule. (The external diameter of the capsule is the externaldiameter of the capsule cap.) Increasing the wall thickness for a givencapsule size is accomplished by using a thinner cap pin, a thinner bodypin and a combination of hotter pin and/or thicker solution. Otherfactors which may be used to increase wall thickness are longer dwelltime in the dipping dishes, more time in the downward position in thespinning section and a modified temperature profile in the gellingstage. For a "0" size capsule, a wall thickness increase ofapproximately 0.0005 inch (0.013 mm) is recommended, yielding a wallthickness of a capsule cap of approximately (0.0042+0.0005)=0.0047 inch(0.119 mm). To increase the wall thickness of a capsule cap by anadditional dimension Δw without increasing the external diameter, it isnecessary to reduce the diameter of the cap pin by approximately 2×Δw.To make the corresponding capsule body it is necessary to reduce thediameter of the body pin by approximately 4×Δw so that the body will fitinto the smaller inside diameter of the cap. Accordingly, for a "0" sizecellulose capsule having a wall thickness as recommended, the cap pindiameter is reduced by 0.001 inch (0.026 mm) and the body pin diameteris reduced by 0.002 inch (0.052 mm) in addition to the reductiondiscussed hereinbelow under "Capsule External Diameter and Pin MoldDiameter." From Table 4, the cut-point diameter of the prior art cap pinis 0.2975 inch (7.56 mm), so an additional reduction 0.001 inch (0.026mm) represents an additional reduction of 0.3%. Again from Table 4, thecut-point diameter of the prior art body pin is 0.2855 inch (7.25 mm),so an additional reduction of 0.002 inch (0.052 mm) represents anadditional reduction of 0.7%.

Alternatively, or additionally, the stiffness of the capsule may beincreased by providing in the capsule body a reinforcing ring, similarto the locking ring, located between the locking ring and the dome ofthe capsule body. This approach provides, for a given capsule wallthickness, a stiffer capsule with a reduced penalty in terms of materialcontent of the capsule body and reduction in interior volume of thefinished capsule. One or more reinforcing rings may be provided.

9. Serial Dipping

An alternative embodiment of the present invention uses serial dippingof pins instead of the batch dipping using a modified Colton machine asdescribed hereinabove. Serial dipping permits every pin to proceedthrough an identical preheat process. This eliminates the need tocompensate for different elapsed time pin-to-pin between preheat anddipping. Dipping one pin at a time would, of course reduce thethroughput rate by a factor of 150 over the embodiment of FIG. 8A inwhich there are thirty pins per bar and five bars are dipped together asa batch. However, it would be possible to mount pins on an articulatedbase (i.e., a chain) one pin per link, and circulate several such chainsin parallel through a preheat process, a dipping process and a dryingprocess on a machine, including an enclosed drying kiln, designed forthe purpose. Another alternative embodiment of the present inventionprovides multiple pins on a bar and transports one bar at a time throughboth the preheat section and the dipping section. In this way thebar-to-bar difference of elapsed time is eliminated and only thedifferential temperature along the bar must be compensated. This couldbe accomplished by a functional equivalent of the split deck.

Solutions to the Problems Unresolved in the Prior Art

A. Analysis of the Problems in the Prior Art

An important contribution of the present invention is the analysis ofthe several unresolved problems in the prior art from the perspective ofeach stage of manufacture and use, as follows:

A1. Preheat

In the Colton machine the most acceptable areas for preheating are thoseprior to the table section where the bars are assembled in groups oftwenty and are stationary for a period during which they can all beheated together. However, the problem with preheating prior to the tablesection is that the action of the table section causes some bars to waitlonger than others for their turn to dip and this can result in somebars cooling more than others prior to dipping, with the cooler barsmaking thinner capsule walls than the other bars. Also, the pins on oneend of the bar might be hotter or cooler than the pins on the other endof the bar simply due to temperature gradients across the machine.

An appropriate place to heat the bars is in the dipper section justprior to dipping. In that section of a traditional Colton dippingcapsule machine, five or more bars are grouped together and then movedas a group over to the dish for dipping in the gel solution. This allowsfor simultaneous heating of a group of bars which avoids the waitingproblem identified above. The only patent to address preheating bars inthe dipper portion of the Colton machine is Chisholm. In the Chisholmpatent, pins are dipped into heated particles which contact the pinsdirectly, heating them to the appropriate temperature for dipping. Thisapproach creates other problems. First, the lubricant coating on the pinprior to dipping is important because cellulose capsules are much moredifficult to remove from the pins than gelatin. Since the lubricant isalready applied at this point in a Colton style capsule machine, the useof a pin-contact heating method results in unreliable capsule removaldue to disturbance of the lubricant layer. Second, there is the problemof lubricant continuing to accumulate in the bead particles, degradingin the heated particles, and being redeposited on the pins at a latertime. Third, there is no room in a traditional Colton machine toaccommodate such a heated particle device. Fourth, no method ofpreheating alone (as opposed to pre-and post-heating) has beensuccessful in making capsules from the Sarkar improved cellulose ofsufficient uniformity for high-speed filling.

A2. Capsule External Diameter and Pin Mold Diameter

For any given standard size of capsule (such as "0", "1", "2", etc.),the size of the pin mold used in the prior art is a well acceptedstandard with little variation in size. The combination of the standardpin mold diameter, accepted standards of wall thickness, and shrinkagecontribute to an overall dimensional standard for the outside diameterof a capsule of a given size which can be accommodated withoutdifficulty on high-speed filling machines where tolerances are tight.

The prior art teaches that the same pin mold may be used for celluloseas is used for gelatin, and there is no prior art that has statedotherwise. However, using the prior art pin for a given capsule sizemakes a cellulose capsule that is often oversized compared the givenstandard size capsule. This causes difficulties in the high-speedfilling machines.

A3. Drying

The traditional drying kilns in the prior art employ plates with holesabove the pins to introduce a stream of air in proximity to the capsules(Wilkie). Blowing air over the pins causes evaporative cooling whichworks well with gelatin since the cooling helps set the gel. However,with cellulose the object is to keep the gel above its thermal gel pointuntil it is thermally set to a sufficient firmness. The traditional(Wilkie) design cools the wet cellulose gel through evaporative cooling,and can cause the gel to flow unevenly and uncontrolled down the moldpin. This makes an uneven capsule which cannot be filled on the precisehigh-speed filling machines.

Further, while some air movement is necessary to remove water vaporreleased during drying, air movement has a tendency to deform capsulesmade of cellulose more drastically than capsules made of gelatin, and adirected stream of air over the capsules can shift the gel before it isfirm.

Blowing air over the exterior of the pins also causes the gel to dryfrom the outside first, causing a "skin" to form which traps moistureinside the film. This can lead to wrinkles or corrugations of thecapsule wall, and subsequent problems on high-speed filling machines.Murphy employed a drying design similar to the Wilkie plates, but hispatent concerns methyl cellulose which is slower drying and less apt tosurface harden. The modified cellulose indicated in the Sarkar patenthas a tendency to dry faster and is prone to deformation when dried inthe conventional way.

Experimental work done by Eli Lilly with the improved Sarkar celluloseshowed that conventional drying design with plates and holes has atendency to cause starred ends and corrugations of the capsule walls.This is a result of compromise in the cellulose formulation, whichimproves dissolution (in the human digestive system) but results infaster release of moisture compared to celluloses used in earliercapsule technology.

Higher temperatures are used in the cellulose drying process than areused in the gelatin drying process. In the prior art drying process, airblows over the pins and escapes to the room. With the highertemperatures of the cellulose drying process, this adds significant heatand heating loads to the room and requires costly air conditioning.

A4. Capsule Removal

With the improved cellulose in the Sarkar patent, removal of the capsulefrom the pin mold is one of the most difficult problems. The traditionalapproach used before the present invention involved a clothespin likedevice, called a stripper. The stripper traveled over the dipped lengthto a position beyond the capsule part. It then closed on the bare pinand moved along the length of the pin until it contacted the edge of thecapsule and subsequently pushed the capsule part off the pin.

The improved cellulose lacks the rigidity necessary for a clean releasefrom the pin when contacted by the stripper cheek. There is a tendencyfor the cellulose part to continue to adhere to the pin and to deformand break under stripper pressure rather than releasing freely.

A further complication in stripping cellulose capsules is the lowmoisture content. Whereas moisture can aid capsule removal in thegelatin process, cellulose capsules become soft at even modest moisturelevels. Thus stripping must always be accomplished under dry capsuleconditions. As with gelatin, dry capsules make capsule removal moredifficult.

Increasing lubrication to aid stripping also poses problems since thecellulose gel is very prone to movement during and immediately after thedip. Excessive lubrication, or even lubricants with particularlyslippery characteristics, have a tendency to cause uneven capsule walls.High temperatures inherent in the process add other constraints to thechoice of lubricant.

A5. Capsule Filling

Lack of uniformity, the sources of which are discussed hereinabove,causes problems on high-speed filling machines. In addition, theflexibility of the improved Sarkar cellulose also causes anotherproblem: being flexible, the capsules are easily deformed out of round.

B. Solution of the Problems in the Prior Art

The problems in each stage of making and using the capsules are solvedin the following manner:

B1. Preheat

Since some bars must wait longer than others to dip, the presentinvention addresses the issue of differential cooling and temperaturecompensation by selectively heating some bars to a higher temperaturethan other bars so that all bars have substantially the same temperaturewhen dipped as a group of five or more. This is accomplished by using apattern of thermally isolated heating elements below the bars (the"split deck") and above the bars (radiant heaters). These heatingelements selectively heat certain bars to predetermined temperatures sothat substantially equal temperatures are achieved at dip.

In addition, the temperature of a bar may vary along its length or frontto back. The split deck allows the selective heating of portions ofbars, those portions which are otherwise repeatedly cooler than otherportions. Thermal sensors are used to maintain the individual heatingareas at an appropriate temperature to consistently deliver all bars andportions of bars at substantially the same dip temperature.

Preheating in the dipper section may be accomplished by heating the pinsby a non-contact heating method which overcomes the problems associatedwith Chisholm's heated particle method. Hot air, radiant elements, etc.may be used in proximity to the pins without disturbing the lubricantlayer, and without the concern of deposits of lubricant on the contactparticles. To accommodate non-contact preheating in the dipper justprior to dip, the present invention modifies the Colton style machine byextending it away from centerline on both the cap side and the bodyside. Also, contact to the back of the bars (away from the pins) may beused to aid preheating in the dipper. Heated elements may be moveddirectly in contact with the back of the bars as sole preheating, or inconjunction with a non-contact heating method applied to the pin side ofthe bar.

To achieve the level of uniformity necessary for high-speed filling,pre-dip heating and post-dip heating are used in conjunction. Post-dipheating continues the gelling process after the dip and assures rapidfirming of the cellulose film. This is accomplished by applying heatdirectly before the dip and directly after the dip and continuing toapply heat for gelation and inside-out drying until the film issufficiently firm.

B2. Capsule External Diameter and Pin Mold Diameter

The apparatus of the present invention includes a pin mold which isundersized to compensate for the differential in shrinkage betweencapsules made from the improved cellulose composition and capsules madefrom gelatin. This results in a cellulose capsule which has the sameoverall diameter and wall thickness as the equivalent gelatin capsule,and is therefore capable of running in existing high-speed fillingmachines.

B3. Drying

The present invention does not use plates with air blowing directly overthe pins, but uses a fully enclosed drying tunnel (kiln), in whichdrying is accomplished by inside-out drying in the most critical stagesof drying. This is accomplished by using heating elements directly underthe deck (or bottom) of the drying tunnel and radiant elements overheadin the drying tunnel, keeping pins above the thermal gel point of thecellulose in the early drying stages. This drives moisture out from theinside. It avoids the skinning over and wrinkling associated with theoutside-in drying of the prior art.

Process air is directed through the enclosed drying tunnel incounterflow to the direction of motion of the pins. The purpose of thecounterflow air is not so much to dry the capsule walls, but rather tomove moisture through the system which has been driven out of thecapsule parts by inside-out drying so the moisture can be exhausted fromthe drying kilns. In this procedure, drier capsules at the end of thedrying tunnel come into contact with dry air which is introduced at theend of the drying tunnel. As the air moves towards the beginning of thedrying tunnel, it picks up moisture. Therefore, wet capsules atbeginning of the drying tunnel come into contact with wet air and driercapsules at the end of the drying process come in contact with drierair. This keeps an appropriate relationship of water vapor pressurebetween capsules and throughput air throughout the drying process toensure even drying. The result is a capsule part without deformation.

In addition, local heating or air agitation is employed to speed dryingin selected areas where the film is sufficiently firm so thatdeformation is not a problem. Full enclosure and insulation of thedrying kilns also prevents heat escaping into the room, thereby avoidingthe higher heating load on the facility that would occur without fullenclosure. This is in direct contrast to the prior art, in which not airis blown over the capsule parts and then escapes into the room.

B4. Capsule Removal

Murphy used the non-modified cellulose, which was rigid enough to beremoved by traditional methods. However, the improved dissolvingcellulose of Sarkar cannot be consistently removed by pushing capsuleparts off the pin by pushing from behind the dipped edge. In the presentinvention, the "stripper" device is modified into a gripper, which hastwo opposed surfaces which grab the capsule above the dipped edge, onthe capsule wall itself, and remove the capsule using pressure to theside walls in conjunction with a motion along the longitudinal axis ofthe pin mold. The Colton machine is modified to allow the grippers toopen wider than normal strippers and the machine is also modified tomove the gripper into a position closer to the closed end of the capsuleso that it contacts on the capsule surface, rather than behind it. Thisaction removes the capsule without damage to the open end, which oftenoccurs when the prior art technique is used on cellulose capsule parts.

B5. Capsule Filling

The flexibility of capsules made from the improved cellulose can causecapsules to malfunction in filling machines, particularly if deformedout of round. The apparatus of the present invention provides a pinwhich is undersized (in the correct amount) to allow a thicker capsulewall, and therefore better rigidity, while maintaining the acceptedoverall diameter of a given standard capsule size, such as "0", "1",etc.

The apparatus of the present invention also provides a body pin whichadds an extra circumferential ring to the capsule body between the lockring and the dome which physically reinforces the capsule wall. One ormore extra rings may be added to increase the overall strength of thecapsule body part, and to assure capsule bodies remain circular.

What is claimed is:
 1. A method of manufacturing pharmaceuticalcellulose capsules of a given size number, the capsules suitable forfilling by capsule filling machines, each capsule consisting of twoparts, a capsule body and a capsule cap, from an aqueous solution of athermogelling cellulose ether composition, using cellulose-capsulebody-side forming pins and cellulose-capsule cap-side forming pins asmolds, comprising the steps of:gelatinizing solution on a pin, includingdipping a pin in the solution to a dip line, to form on the pin acapsule part of gelatinized solution; drying the capsule part on thepin; removing the capsule part from the pin; transporting a plurality ofpins through the steps of gelatinizing, drying and removing, in a closedpath; using a cellulose-capsule forming pin having a cut-point diameterthat is smaller than a corresponding cut-point diameter of acorresponding gelatin-capsule forming pin used for manufacturing acorresponding gelatin capsule part of the given size-number; and sizingthe cellulose capsule forming pin so as to make a cellulose capsule partthat has substantially the same overall diameter as the correspondinggelatin capsule part of the given size-number and a greater wallthickness than the wall thickness of the corresponding gelatin capsulepart of the given size-number.
 2. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2775-0.2815 inch (7.05-7.15 mm) to make a cellulose capsulebody for an "0" size capsule.
 3. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2905-0.2945 inch (7.38-7.48 mm) to make a cellulose capsulecap for an "0" size capsule.
 4. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.3105-0.3173 inch (7.89-8.06 mm) to make a cellulose capsulebody for an "00" size capsule.
 5. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.3276-0.3332 inch (8.32-8.46 mm) to make a cellulose capsulecap for an "00" size capsule.
 6. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2503-0.2557 inch (6.36-6.50 mm) to make a cellulose capsulebody for a "1" size capsule.
 7. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2622-0.2667 inch (6.66-6.77 mm) to make a cellulose capsulecap for a "1" size capsule.
 8. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2289-0.2339 inch (5.81-5.94 mm) to make a cellulose capsulebody for a "2" size capsule.
 9. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2397-0.2438 inch (6.09-6.19 mm) to make a cellulose capsulecap for a "2" size capsule.
 10. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2095-0.2140 inch (5.32-5.44 mm) to make a cellulose capsulebody for a "3" size capsule.
 11. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.2202-0.2240 inch (5.60-5.69 mm) to make a cellulose capsulecap for a "3" size capsule.
 12. A method according to claim 1, using abody-side cellulose capsule forming pin having a cut-point diameter inthe range 0.1900-0.1941 inch (4.83-4.93 mm) to make a cellulose capsulebody for a "4" size capsule.
 13. A method according to claim 1, using acap-side cellulose capsule forming pin having a cut-point diameter inthe range 0.1997-0.2031 inch (5.07-5.16 mm) to make a cellulose capsulecap for a "4" size capsule.
 14. A method of manufacturing pharmaceuticalcellulose capsules of a given size number, the capsules suitable forfilling by capsule filling machines, each capsule consisting of twoparts, a capsule body and a capsule cap, from an aqueous solution of athermogelling cellulose ether composition, using cellulose-capsulebody-side forming pins and cellulose-capsule cap-side forming pins asmolds, each cellulose-capsule forming pin having an elongated pin body,a domed head located at one end of the pin body, and a substantiallycylindrical sidewall surrounding the pin body and extending from thedomed head, the substantially cylindrical sidewall having a diameter,the method comprising the steps of:gelatinizing solution on a pin,including dipping a pin in the solution to a dip line, to form on thepin a capsule part of gelatinized solution; drying the capsule part onthe pin; removing the capsule part from the pin; transporting aplurality of pins through the steps of gelatinizing, drying andremoving, in a closed path; and using a cellulose-capsule forming pinthat is undersized with respect to a corresponding gelatin-capsuleforming pin used for manufacturing a gelatin capsule part of the givensize number, the diameter of the substantially cylindrical sidewall ofthe cellulose-capsule forming pin being smaller than a correspondingdiameter of a substantially cylindrical sidewall of the correspondinggelatin-capsule forming pin, the cellulose-capsule forming pin sized soas to make a cellulose capsule part that has substantially the sameoverall diameter as a corresponding gelatin capsule part of the givensize-number.
 15. A method according to claim 14, using acellulose-capsule forming pin to make a cellulose capsule cap for an "0"size capsule, the cellulose-capsule forming pin undersized by an amountin the range of approximately 0.002-0.006 inch (0.05-0.15 mm).
 16. Amethod according to claim 14, the cellulose-capsule forming pin sized soas to make a cellulose capsule part that has substantially the sameoverall diameter as the corresponding gelatin capsule part of the givensize-number and a greater wall thickness than a corresponding wallthickness of the corresponding gelatin capsule part of the givensize-number.
 17. A method according to claim 16, for forming a thickwall cellulose capsule body, wherein the diameter of the substantiallycylindrical sidewall of the cellulose-capsule forming pin is smallerthan the diameter of the substantially cylindrical sidewall of thecorresponding conventional gelatin-capsule forming pin by approximately1.3 percent.
 18. A method according to claim 16, for forming a thickwall cellulose capsule cap, wherein the diameter of the substantiallycylindrical sidewall of the cellulose-capsule forming pin is smallerthan the diameter of the substantially cylindrical sidewall of thecorresponding conventional gelatin-capsule forming pin by approximately1.6 percent.
 19. A method according to claim 14, wherein gelatinizingsolution includes dipping a hot pin into the solution.
 20. A methodaccording to any of claims 14-19, for making a cellulose capsule part ofany one of sizes "000", "00", "1", "2", "3", "4" and "5", thecellulose-capsule forming pin undersized proportionally.